Added CRU operations in searchForFreeSlots display. Requires testing.
Added undo support for tick command
Allows normal operations on searchFreeSlots display and show up to date
information
Merge branch 'Logic' of https://github.com/cs2103aug2014-w15-3J/Ticker.git into Logic
Edited undoManager for searchFreeSlot's take method
Merge pull request #112 from cs2103aug2014-w15-3J/Logic

Merge Master with Logic